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In routine small-molecule single crystal structure determination, accurate absolute structure determination has sometimes been challenging. Developments in diffractometers, X-ray sources, detectors and software, along with new concepts for the elucidation of the absolute structure have seen the greatest advances in recent times. Nonetheless, determining the absolute structure of a crystal, particularly when only light atoms are present, requires some thought in the planning of the experiment in order to obtain the best possible data and some care in modelling the structure and interpreting the results so as not to draw incorrect or unsupported conclusions. Some practical recommendations for best practice and how to avoid pitfalls and misinterpretations are presented as a guide, particularly for those new to the field of crystal structure analysis.

Enantiomerically pure C1 and C2-symmetric bidentate N,N- and N,P-ligands are accessible from (+)-camphor in good yields (60–90%). Modified syntheses of precursors 1 and 2 are disclosed as well as the crystal structures of three hydroxy-pyrazoline intermediates. Ligands 3, 4, 6, and 11 were fully characterized including an X-ray crystal structure of C2-symmetric 6, which showed an E-configuration in the solid state. These ligands form complexes with Ni(II), Pd(II), and Rh(I) in good yields (84–96%); the X-ray crystal structures of complexes 12, 14, and 16 confirmed the bidentate coordination modes of ligands 4, 6, and 11 and distorted tetrahedral [for Ni(II)] and square planar [for Rh(I)] coordination geometries. Furthermore, the structure of the Rh(I) complex 16 revealed the presence of a Ph2PCl ligand, which, along with spectroscopic data, is proof of an almost quantitative P–N bond cleavage upon coordination of ligand 11 to [RhCl(COD)]2.

Hydrothermal synthesis has been used as a soft chemical method to prepare bismuth molybdate catalysts for the selective oxidation of propylene to acrolein. All obtained samples displayed a plate-like morphology, but their individual aspect ratios varied with the hydrothermal synthesis conditions. Application of a high Bi/Mo ratio during hydrothermal synthesis afforded γ-Bi 2 MoO 6 as the main phase, whereas lower initial bismuth contents promoted the formation of α-Bi 2 Mo 3 O 12 . Synthesis with a Bi/Mo ratio of 1:1 led to a phase mixture of α- and γ-bismuth molybdate showing high catalytic activity. The use of nitric acid during hydrothermal synthesis enhanced both propylene conversion and acrolein yield, possibly due to a change in morphology. Formation of β-Bi 2 Mo 2 O 9 was not observed under the applied conditions. In general, the catalytic performance of all samples decreased notably after calcination at 550 °C due to sintering.

A convenient synthesis of (S)-proline hydrazide 2a via the reaction of ethyl (S)-N-benzylprolinate with hydrazine hydrate and subsequent deprotection of (S)-N-benzyl proline hydrazide 5 is described. The latter, in methanolic solution, reacted with aromatic aldehydes as well as with cycloaliphatic ketones at room temperature to give the corresponding hydrazones of type 7 in good yields. The structure of the product with furan-2-carbaldehyde 7b, proving the (E)-configuration of the hydrazone, was established by X-ray crystallography. In the case of the unprotected (S)-proline hydrazide 2a, the analogous reaction with aromatic aldehydes led either to the expected hydrazones 7 or the 1H-pyrrolo[1,2-c]imidazol-1-one derivatives 8, depending on the reaction conditions. The latter were formed via a secondary cyclocondensation of the initially formed 7 with a second molecule of the aldehyde. Whereas the reaction of (S)-N-benzyl proline hydrazide 5 with butyl isocyanate and isothiocyanate gave the corresponding semicarbazide and thiosemicarbazide, respectively, of type 9, the unprotected (S)-proline hydrazide 2a yielded the 1:2 adducts 10. Thiosemicarbazide 9b underwent cyclization reactions under basic (NaOH) and acidic (H2SO4) conditions to yield (S)-prolinyl-substituted 1,2,4-triazole-3-thione 11 and 1,3,4-thiadiazole-2-amine 12, respectively.

BiVO4 has attracted research interest as one of the most promising visible-light-driven oxidic photocatalysts for water splitting and wastewater treatment. Highly crystalline BiVO4 particles with a homogeneous morphology are now available from a straightforward, one-step hydrothermal protocol. The facile morphology control of BiVO4 particles in the Bi(NO3)(3)center dot 5H(2)O/V2O5/K2SO4 hydrothermal system is achieved through K2SO4 as an inorganic additive that brings forward materials with a high photocatalytic activity. BiVO4 particles generated from this inorganic additive-assisted approach outperform BiVO4 materials obtained via other preparative routes in the decomposition of methylene blue (MB) under visible light irradiation. The relations between morphology, crystallinity and photocatalytic O-2 evolution in the presence of AgNO3 and FeCl3 as sacrificial reagents were studied with respect to the hydrothermal optimization of material properties. Furthermore, the Bi(NO3)(3)center dot 5H(2)O/V2O5/K2SO4 hydrothermal system brings forward potassium vanadate fibers as a second phase that also exhibits promising photocatalytic properties with respect to the decomposition of MB in the presence of visible light. (C) 2009 Elsevier B.V. All rights reserved.

—(R)- and (S)-[(benzyloxy)methyl](tert-butyl)methylsilane [())-(R)-1 and (+)-(S)-1], possessing a stereogenic center at theSi-atom, were prepared in highly enantiomerically enriched form by resolution via diastereomeric silyl ethers. Conversion of thehydrosilanes into different functionalized chiral silanes by direct or stepwise substitution of the (Si)–H-atom was shown to proceedwith high stereoselectivity (96–98% stereoselectivity under optimized conditions) thus allowing the preparation of substrates wherethe chiral silicon moiety can act as a chiral auxiliary for stereoselective transformations. 2004 Elsevier Ltd. All rights reserved. 1. IntroductionWe have previously shown that chiral silicon groups canefficiently be used as chiral auxiliaries for stereoselectivetransformations. 1–6 Of particular interest was silicongroup A containing a ‘Si-centered’ stereogenic, whichwas used as an auxiliary for the asymmetric nucleophilicaddition of organometallics to the carbonyl groups ofacylsilanes 2

The primary reason why the RuO 2 (1 1 0) surface is much more active in the oxidation of CO than the corresponding metal Ru(0 0 0 1) surface is correlated with the weaker oxygen bonding on RuO 2 (1 1 0) compared to chemisorbed oxygen on Ru(0 0 0 1). The RuO 2 (1 1 0) surface stabilizes at least two potentially active oxygen species, i.e., bridging O and on-top O atoms. Together with various adsorption sites for CO during the reaction, the CO oxidation reaction over RuO 2 (1 1 0) becomes quite complex. Using the techniques of temperature programmed reaction and desorption in combination with state-of-the-art density functional theory calculation we studied the CO oxidation reaction over RuO 2 (1 1 0) in the temperature range of 300–400 K. We show that the CO oxidation on RuO 2 (1 1 0) surface is not dominated by the recombination of CO with on-top O, although the binding energy of the on-top O is 1.4 eV lower than that of the bridging O atom.